The present invention relates generally to electrical power transmission and distribution networks and more particularly to a system for monitoring electrical characteristics of protective relay systems and determining abnormal operating conditions.
Electrical power is typically produced at centralized power production facilities and transferred at high voltages to local substations. The local substations transform the electrical power to a medium or low voltage. The electrical power is subsequently distributed through feeders to local distribution networks.
Electrical utilities have a number of metrics that are used to track performance and customer satisfaction. These metrics, which include the system average interruption frequency index (“SAIFI”), the customer average interruption duration index (“CAIDI”), and for some utilities, the momentary average interruption frequency index (“MAIFI”). SAIFI measures the average number of interruptions that a customer would experience during a time period, such as a year. CAIDI measures the duration of the interruption that a customer would experience, and is generally a few hours per year. MAIFI measures the number of power interruptions that have a duration of less than five minutes that a customer would experience during a given time period. Some or all of these metrics are also used by government regulators to aid in determining if the electrical utility is adhering to the regulations in maintaining a durable and reliable electrical service.
Thus, it is desirable for the utilities to monitor the health and performance of their electrical network to ensure customer satisfaction and compliance with governmental regulations. Advanced electrical networks, sometimes referred to as “Smart Grid” apply advanced sensors and two-way communications technologies to keep track of the network operations from the generation plant to the electrical outlets in a customers residence. When fully implemented, the Smart Grid will allow for generators, distribution equipment and loads to interact in real time. Electrical demand or variances in electrical characteristics may then be actively managed, reducing wear on equipment and improving reliability.
The ability of these advanced sensors to monitor and record electrical characteristics provides the electrical utilities with a large amount of information, including but not limited to voltage, current, real power, and reactive power for example. When the sensor network is expanded to monitoring many electrical circuits, the large volume of information becomes difficult for electrical utility personnel to utilize. This problem increases in complexity as the sampling rate of the sensor network becomes larger.
One of the impediments to the implementation of Smart Grid is the existence of legacy systems and equipment, such as electromechanical relays for example. This equipment is in widespread use making replacement costly and time consuming. One further difficulty is that this equipment is often difficult to retrofit with modern communications capability. As a result, when protective equipment, such as a protective relay for example, is activated, utility personnel must travel to the location and manually inspect the equipment. Often the only indication will be a mechanical visual indicator, sometimes referred to as a “target flag.” Where monitoring equipment is available for protective relays, the data provided only provides limited insight to utility personnel.
Thus, while existing electrical network monitoring systems are suitable for their intended purpose, there remains a need for improvements. In particular, there remains a need for improvement regarding the ability to monitor and analyze information collected from sensors coupled to protective relay systems to detect and identify abnormal operating conditions.